How do I specify different Layouts in the ASP.NET MVC 3 razor ViewStart file?

You could put a _ViewStart.cshtml file inside the /Views/Public folder which would override the default one in the /Views folder and specify the desired layout:

@{
    Layout = "~/Views/Shared/_PublicLayout.cshtml";
}

By analogy you could put another _ViewStart.cshtml file inside the /Views/Staff folder with:

@{
    Layout = "~/Views/Shared/_StaffLayout.cshtml";
}

You could also specify which layout should be used when returning a view inside a controller action but that’s per action:

return View("Index", "~/Views/Shared/_StaffLayout.cshtml", someViewModel);

Yet another possibility is a custom action filter which would override the layout. As you can see many possibilities to achieve this. Up to you to choose which one fits best in your scenario.

---

UPDATE:

As requested in the comments section here’s an example of an action filter which would choose a master page:

public class LayoutInjecterAttribute : ActionFilterAttribute
{
    private readonly string _masterName;
    public LayoutInjecterAttribute(string masterName)
    {
        _masterName = masterName;
    }

    public override void OnActionExecuted(ActionExecutedContext filterContext)
    {
        base.OnActionExecuted(filterContext);
        var result = filterContext.Result as ViewResult;
        if (result != null)
        {
            result.MasterName = _masterName;
        }
    }
}

and then decorate a controller or an action with this custom attribute specifying the layout you want:

[LayoutInjecter("_PublicLayout")]
public ActionResult Index()
{
    return View();
}